This invention relates to a method and apparatus for performing corrective techniques on the eye and more particularly to a system, for use with a surgical microscope, for viewing the eye while performing corrective techniques and at the same time displaying comparative images of indicia related to the present shape of the eye and a predetermined eye shape.
Present systems for viewing the eye during surgical techniques involve the use of a surgical microscope for real time viewing and usually, intermittent keratometer measurements before, during and after surgery. This procedure is not only slow and thus time consuming, its accuracy is minimal in that equipment must be moved into and out of the surgical field with each usage. In additional this procedure must take into account the sterile atmosphere of the surgical location and the constant interfacing of measuring equipment with the sterile field. Such a surgical technique might typically follow the pattern of preoperative quantitative keratometer measurement is made to determine what effect the operative procedure has had on the eye. Next suturing is often performed to close incisions in the eye and post-operative keratometer readings are taken to determine the condition of the sutured eye. Each keratometer reading involves the replacement of instrumentation within the surgical field and in precise position with respect to the eye. The preciseness of repositioning of such instrumentation will of course have an effect on the quantitive accuracy of the comparative readings. Additionally present keratometers measure approximately only a 3 mm chord across the center of the eye. The corrective technique of concern in this application more often deals with distortions on the corneal surface between the 2 to 12 mm chords.
An improvement on the above described technique is suggested by mounting a quantitative keratometer on a surgical microscope. The Troutman keratometer exemplifies this manner of treating the problem. The Troutman device is described at pages 28 to 32 of Microsurgery of the Anterior Segment of the Eye Vol. II, C. V. Mosby Company, 1977. The Troutman keratometer is characterized by a twelve point light source mounted in a ring about the microscope body. Light is projected to twelve points on the cornea. A keratometer reticle is fitted to the eye piece for the surgeons nondominant eye. It has two concentric circles for reference to the keratometer projection, and split cross hairs to align sutures and mark an astigmatic axis. The Troutman keratometer is a qualitative measuring instrument with a function very different from that of a keratoscope, which is designed for measuring corneal topography. The Troutman keratometer on the other hand is designed specifically to aid the surgeon in the interpretation and correction of meridianal corneal errors. It approximates the powers of astigmatic bands by offering a comparison of reticle circles to an oval reflection of the projected light ring. Interpretation of the projection is a qualitative matter depending on the experience of the surgeon. Keratometer mire patterns are so distorted in the early postoperative course as to be of little value in making determinations concerning refraction. Thus, no present technique or system is available to facilitate accurate determination of corneal topography in a real time intraoperative situation. Also lacking is a system offering a conveniently usable comparison of real time intrasurgical data with cursor indicia indicative of a predetermined or preoperative condition.
It is therefore an object of the present invention to provide a new and improved method and apparatus for providing simultaneously on a convenient viewing surface, real time quantitative data relating to the present corneal topography, and predetermined data relating to a preoperative condition or desired corneal surface condition, with such system being arranged for use intraoperatively in conjunction with a surgical microscope.